1. Field
The present application relates to a structured illumination apparatus, a structured illumination microscopy apparatus, and a pattern projection type profile measuring apparatus capable of realizing a super resolution in an in-plane direction.
2. Description of the Related Art
A super-resolution microscope is one that modulates an illumination light flux that illuminates a sample plane and demodulates an image-forming light flux which is incident on a position that is substantially conjugated with the sample plane of an image-forming optical system, in order to make information regarding a high spatial frequency that exceeds a resolution limit (diffracted light at a large angle) out of diffracted light that outgoes from a sample, to be contributed to an image formation (refer to Non-Patent Document 1: W. Lukosz, “Optical systems with resolving powers exceeding the classical limit. II”, Journal of the Optical Society of America, Vol. 57, PP. 932, 1967; Patent Document 1: Japanese Unexamined Patent Application Publication No. H11-242189; Patent Document 2: Specification of U.S. Pat. No. RE 38307; Patent Document 3: U.S. Patent Application Publication No. 2009/0219607; and the like).
In a method of Non-Patent Document 1, a diffraction grating (diffraction grating for modulation) is disposed in the vicinity of a sample plane, and a diffraction grating (diffraction grating for demodulation) having a grating constant which is conjugated with that of the diffraction grating for modulation, is disposed at a position which is substantially conjugated with the sample plane of an image-forming optical system. When those two diffraction gratings are moved in a conjugated manner, it becomes possible to observe a structure of sample by separating it from patterns of the diffraction gratings.
Meanwhile, Patent Document 1 discloses an example in which a structured illumination microscope is applied to a fluorescent observation. In a method of Patent Document 1, a light flux that outgoes from a coherent light source is split into two light fluxes by a diffraction grating, and those two light fluxes are individually condensed on mutually different positions on a pupil of objective lens. At this time, the two light fluxes outgo from the objective lens as collimated light fluxes with different angles, and overlap each other on a sample plane to form striped interference fringes. Accordingly, the sample plane is subjected to structured illumination. Further, in the method of Patent Document 1, images of sample images are repeatedly obtained while shifting a phase of the structured illumination in steps, and calculation corresponding to the aforementioned separation (separating calculation) and calculation corresponding to the aforementioned demodulation (demodulating calculation) are performed on the obtained plurality of images.
Incidentally, as a method of shifting the phase of structured illumination in steps, there are a method in which a wedge-shaped prism is inserted into one of the above-described two light fluxes and moved in steps in a direction perpendicular to an optical axis, a method in which a diffraction grating is moved in steps in a direction perpendicular to a grid line, a method in which a sample is moved in steps in a pitch direction of structured illumination, and the like.
Further, in a method of Patent Document 2, images of sample images are repeatedly obtained while changing a direction of structured illumination in steps, to thereby achieve a super-resolution effect over various directions. Incidentally, as a method of changing the direction of structured illumination in steps, there is a method in which a diffraction grating or a sample is rotated in steps around an optical axis by a rotation motor or the like.
Particularly, in the method of Non-Patent Document 2: Olga Gliko et al., “Development of fast two-dimensional standing wave microscopy using acousto-optic deflectors”, Proc. of SPIE Vol. 6861 68610B-8, four acousto-optical elements are used to change the direction or a phase of the structured illumination.
However, when an optical element is moved in steps, a certain period of time is required for stopping the moving optical element at an appropriate position, so that it is difficult, in the method of Patent Document 2, to reduce a period of time required to completely obtain the required images. Particularly, when a sample being an observational object is an organism specimen, there is a chance that a structure of the sample changes every second, so that the obtainment of images should be performed as fast as possible.
Further, in a method of using four acousto-optical elements as the method of Non-Patent Document 2, an optical system of a super-resolution microscope becomes complicated, and due to the complication of the system, there is a disadvantage in the aspect of the adjustment of the optical system and the cost.
Accordingly, the present application has a proposition to provide a structured illumination apparatus having a configuration suitable for increasing a speed of obtaining images, an efficient structured illumination microscopy apparatus, and an efficient profile measuring apparatus.